A073488 Squarefree numbers having exactly two prime gaps.

110, 130, 170, 182, 190, 230, 238, 266, 273, 290, 310, 322, 357, 370, 374, 399, 406, 410, 418, 430, 434, 470, 483, 494, 506, 518, 530, 546, 561, 574, 590, 598, 602, 609, 610, 627, 638, 651, 658, 670, 682, 710, 714, 730, 741, 742, 754, 759, 777, 782, 790

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

A073484(a(n)) = 2.

Example

1430 is a term, as 1430 = 2*5*11*13 with two gaps: between 2 and 5 and between 5 and 11.

Mathematica

q[n_] := SequenceCount[FactorInteger[n][[;; , 1]], {p1_, p2_} /; p2 != NextPrime[p1], Overlaps -> True] == 2; Select[Range[800], SquareFreeQ[#] && q[#] &] (* Amiram Eldar, Apr 10 2021 *)

Crossrefs

Cf. A005117, A073486, A073487, A073489, A073494.

Sequence in context: A059469 A114068 A073494 * A244389 A176879 A039447

Adjacent sequences: A073485 A073486 A073487 * A073489 A073490 A073491

Keyword

nonn

Author

Reinhard Zumkeller, Aug 03 2002

Status

approved